In the first book, casters felt like force multipliers. Immensely valuable, but you still needed armies and warlords to do the actual legwork. Then it was established that casters can't be popped on purpose - when Jetstone lost its Dollamancer, they thought they couldn't get another one before Ace actually did pop. The apparent revelation that there's desperate casters in MK who'd do anything just for stable upkeep feels... weird, but I didn't read that story.